Theoretical and experimental psychoacoustic research oriented toward the creation of a coherent, quantitative, and unified theory of intensity perception and loudness is proposed. This research is a continuation of previous research by the same investigators and involves the development and/or integration of models of decision-making, sensory processing, short-term memory, and perceptual-context effects; experiments on discrimination, identification, and scaling of sound intensity; analyses of data processing procedures for estimation of parameters and for choosing between alternative theories; and exploration of applications to other areas of psychophysics, to the study of hearing impairments, to the perception of speech signals, and to problems associated with noise pollution.